With bewildering speed Mr. Putin officially recognized Crimea's self-declared independence and prepared a treaty on its accession. After laying out his logic in a defiant speech to Russian lawmakers in the Kremlin on Tuesday afternoon, Putin stepped into the adjacent room and signed the treaty in a brief ceremony with the pro-Russian leaders of Crimea.

And that's how Crimea, as far as Russia is concerned, became its 84th region.

In Moscow's playbook, Crimea will now enter Russia as an autonomous republic, with its own parliament and president. Legal formalities will be completed in the next few days, and a transitional period (scheduled to run until Jan. 1, 2015) will be dedicated to resolving the numerous logistical problems the switch will entail, such as the move to a new currency, a different legal system, and a mass exchange of citizenships.

But the result will not be accepted in the European Union and the US — and could bring a redefining of their relations with Russia. They call the Crimean referendum illegitimate and view Russia's annexation of the territory as a dangerous precedent, since no major international player has bitten off and swallowed a piece of another country in the 21st century.

Until now.

"Over the past 20 years relations between Russia and the West have not brought the results Moscow hoped for, so it's clear that Putin decided it's time to change the terms," says Fyodor Lukyanov, editor of Russia in Global Affairs, a leading Moscow foreign policy journal.

"Why the haste?" he says. "Well, what was there to wait for? Doing it fast suited the Russian and the Crimean authorities. As for political consequences and the threat of sanctions from the West — well, it appears we're ready to pay the price."

What about eastern Ukraine?

In his speech, Putin praised the Crimean voters for their "brave choice" and made clear that the territory's inclusion in Russia is now irreversible. "Russia could not but respond to Crimea's request for help, otherwise it would have been betrayal," he said.

But in what might be interpreted as a concession to Ukraine, Putin pledged that Russia would not seek to grab any more territory from its restive and largely Russian-speaking eastern regions. "Don’t believe those who say Russia will take other regions after Crimea. We don’t need that," Putin said.

He said Russia will henceforth use "political, diplomatic, and legal" means to defend the rights of Russian-speakers in Ukraine.

These words remain to be tested as many of these eastern regions experience rolling protests against the Western-leaning interim government in Kiev. Putin has repeatedly spoken out in favor of interfering when Moscow deems the rights of ethnic Russians and Russian compatriots to be under threat, and crowds of demonstrators across eastern Ukraine have been calling on the Kremlin to step in on their behalf.

Snap polls, cited by Putin, suggest that the vast majority of Russians are delighted by the reunification with Crimea, which had belonged to Russia for over 200 years until Soviet leader Nikita Khrushchev "gifted" it to Ukraine in 1954. After the breakup of the USSR, the territory remained part of Ukraine, even though ethnic Russians comprised 60 percent of its population and Russian was the universal everyday language.

Russians have long considered Crimea unfinished business. Few appear to regret that Ukraine's recent street-backed political upheaval, and the resultant power vacuum in Kiev, gave Moscow the opportunity or excuse to snatch back the peninsula.

“This was a long time coming, but it was inevitable. It was always going to happen one day," says Pyotr Romanov, a political expert with the now-disbanded official RIA-Novosti news agency.

The ball in the West's court

In his address to parliament, Putin slammed the West, particularly the US, for citing international law when convenient while pursuing might-makes-right policies when it suited their own interests. He insisted ardently that Crimea's hasty referendum and its accession to Russia are completely in line with global legal norms; but in the view of some Russian experts, Putin is dishing the West a dose of its own medicine.

"Who hasn't broken international law in the post-World War II period?" says Mr. Romanov.

Still, Russians are liable to wake up to a new world in the next few months, as international opposition to the Crimea annexation hardens, and as sanctions imposed by the West possibly deepen and start to bite.

"This will not go well. Russia will strengthen Crimea while the West will feel free to make the rest of Ukraine its protectorate," says Alexei Makarkin, deputy director of the independent Center for Political Technologies in Moscow.

The consequences will almost certainly include efforts by Europe to diversify its energy supplies away from reliance on Russia, as well as other measures that will drag down Russia's already stagnating economy, he says.

And the domestic political consequences of USSR-like isolation are likely to be dire as well, he adds.

"We are already seeing a change in the tone of domestic politics. Those few who opposed Crimea being joined to Russia are openly called 'traitors.' Opposition that criticizes the authorities from outside the system are going to face a lot of new problems," he adds.